The present invention relates to an electrophotographic receptor, and more particularly, to a photoreceptor suitable for improving printing service life.
Although primarily inorganic materials such as selenium, zinc oxide, cadmium sulfate and titanium oxide were used for photoconductive materials used in electrophotographic receptors of the prior art, these materials were unsatisfactory in terms of sensitivity, heat resistance and printing durability, and also had problems with respect to toxicity. On the other hand, electrophotographic receptors having a photosensitive layer consisting primarily of an organic photoconductive compound are generally superior to inorganic types in terms of having less toxicity and greater transparency, flexibility and freedom of shape.
In the case of using an electrophotographic printer employing the Carlson method, printing is performed by means of processes consisting of electrification, exposure, development, transfer, separation and fixation. However, electrification, exposure, development and transfer are normally performed on a photoreceptor. Consequently, although organic photoreceptors have the remarkable advantages described above, they have the shortcoming of wearing down quickly in the form of reduced charge potential and changes in sensitivity accompanying repetition of the processes of electrification and exposure. This is due to deterioration of the photoreceptor surface due to mechanical factors such as abrasion, and chemical factors such as being subjected to an oxidizing atmosphere such as ozone produced during corona electrical charging in processes using the Carlson method.
Although a method using an antioxidant is proposed in Japanese Unexamined Patent Publication No. 122444/1982 as a means of preventing surface deterioration caused by ozone and so on, this method is not satisfactory. In photoreceptors wherein charge generating substances are present in the outermost layer, it becomes easy for ozone and so on to be adsorbed by the charge generating substance thereby making measures for preventing surface deterioration increasingly difficult.